Saturday, November 30, 2013

Most of what you read about Utah snow is entirely bogus and makes little sense meteorologically. Yet another example of Zombie meteorology that needs to die is an article by Jeff Layton in the latest Alaska Airlines Magazine entitled Lake Effect:

It’s almost unfair that Salt Lake City has so much excellent skiing at its doorstep, but there is a scientific explanation, my friend Andy Mars told us the next day as we rode one of Brighton’s lifts. The Wasatch mountain rise up from the east edge of town, and the massive Great Salt Lake flanks the city to the west. Winter storms extract moisture from the lake - which doesn’t freeze. The salinity of the lake water gives the snowflakes unique powdery properties, and they pike up in totals that regularly exceed 500 inches per season.

While it is true that Salt Lake City has a lot of excellent skiing at its doorstep, and the average snowfall in portions of upper Little Cottonwood and Big Cottonwood exceeds 500 inches, just about everything else about this paragraph is wrong. Scientific studies have shown that lake-effect storms produce only about 5% of the total precipitation in the Cottonwoods from mid September through mid May. The idea that the salinity in the lake gives snowflakes unique powdery properties is equally bogus. You can find drier snow in Colorado. What makes powder skiing in Utah so great isn't that the snow is unusually dry, but that we get a lot of it and it frequently comes in storms that produce right-side up snowfalls (meaning that we get a lot of storms that produce heavier, higher density snow at the beginning and lighter lower density snow at the end).

Stick with the Wasatch Weather Weenies to avoid the Zombie meteorology apocalypse.

Friday, November 29, 2013

I was curious how the Thanksgiving day holiday would affect air quality in the Salt Lake Valley. Answer: Not much. PM2.5 levels continued to climb yesterday, with hourly averages peaking at 42 ug/m3 late yesterday and 24-h averages continuing to climb to 27 ug/m3.

Source: Utah Division of Air Quality

Thus, Black Friday is aptly named this year. There is a weak trough pushing into northern Utah for the weekend. Hopefully it will stir things up a bit and provide some relief for the valley before the holiday weekend comes to a conclusion. If not, there's always the mountains.

Personally, I feel fortunate to be out of town and breathing the cleanest air on Earth in southeast Alaska. It is the rainy season here, but the car-wash-like conditions let up just enough to allow us to take a beautiful hike before overindulging on turkey and trimmings. Happy belated Thanksgiving.

Tuesday, November 26, 2013

There will be no snow in Utah on Thanksgiving Day. That's good news for everyone driving to Grandmama's house. Right now, the first part of Thanksgiving weekend (Thursday and Friday) looks pretty benign meteorologically, but with some degraded air quality in the urban valleys. There's a chance of some valley rain and mountain snow showers later in the weekend, but right now it doesn't look like it is going to add up to much. Nevertheless, keep an eye on the forecast if you are traveling.

For skiers, I'm sorry to say that this looks to be a weekend with snow primarily from hoses not heaven. Natural snowpack in the upper elevations of the Wasatch presently sits at 50-85% of average. At SNOTEL sites, Snowbird has the most robust snowpack with 4.4 inches of snow water equivalent (green line below). That's actually right on the median for this time of year, meaning that half of the years have more, half have less. Of course, by the time we get to turkey day, we will be slightly below the median.

Source: NWS/CBRFC

In search of a deeper snowpack? Have a looksee at the map below, but beware as there are some spurious individual observations.

Source: NRCS

Upper elevations of the Park Range near Steamboat Springs and the Sierra Madre extending into Wyoming include several SNOTEL stations with bigger SWE numbers than Snowbird:

Rabbit Ears Pass, 9400 ft: 6.9 inches

Dry Lake, 8400 ft: 5 inches

Tower, 10,500 ft: 11.2 inches

Whiskey Park, 8950 ft: 8 inches

Old Battle, 10,000 ft: 8 inches

Snowdepth at the Tower Snotel is 40 inches. That's nice, but keep in mind that is near the summit of the southern Park Range, so it's probably the deepest snowpack in that neighborhood.

Long range forecasts suggests a shift in the pattern next week. Keep your fingers crossed.

Sunday, November 24, 2013

With all quiet on northern Utah's eastern and western front this morning, and generally benign weather expected the first few days of Thanksgiving week, our gaze turns eastward to upstate New York and the Tug Hill Plateau where we are now gearing up for the National Science Foundation sponsored Ontario Winter Lake-effect Systems (OWLeS) project (see also The OWLeS Field Program: Adventures on the Tug Hill Plateau).

Although there have been some lake effect rain and "slush" events during the past couple of weeks, The Tug Hill just had its first significant, widespread dumpage, so our excitement level is rising.

I suspect most Utahns won't bother making the trip (ha ha), but I know we have some upstate New York readers and if they are interested they can visit the media day and open house that will be held at Penn Yan Airfield near Geneva on December 4. Click here for more information. Tours of the Wyoming King Air research aircraft and Doppler on Wheels mobile radars will be included.

We have already installed some of our equipment on the plateau, but our "advance" team will be departing Salt Lake on Saturday November 30 to begin the long drive to upstate NY and get the rest of our equipment installed in time for the first potential day of field-program operations on December 5th. I'm currently negotiating with the weather gods for a snow-free trip for the team.

Saturday, November 23, 2013

Continuing with the living dead theme of the previous post, this is starting to turn into the zombie downslope windstorm. It just won't die. The UDOT portable tripod along SR-89 near Lagoon just had a wind gust to 67 miles per hour.

Source: MesoWest

Strong winds also persist from Olympus Cove to the University of Utah along the east bench of the Salt Lake Valley.

Source: MesoWest

Such winds aren't as strong as observed on Thursday night, but I'm sure they are getting annoying for those living in affected areas.

Friday, November 22, 2013

We are currently in a "lull" with regards to the strength of the downslope winds, but the Big Bad Wolf is expected to regain his lung capacity with the winds expected to intensify later today. The National Weather Service has thus extended the high wind warning to noon Saturday.

Source: NWS

Gusts yesterday fell short of those observed in the 1 December 2011 event, but nonetheless were impressive and caused problems for travel by high profile vehicles along the Legacy Parkway and I-15. The highest gusts (80 mph) were observed in the Centerville–Farmington area. The 62 mph gust at the University of Utah is quite impressive. I can't recall what our record is (maybe ~70 mph), but I always use 60 mph as the threshold for a significant event.

Source: NWS

Strong easterly winds along the Wasatch Front come in two major varieties:

Gap winds or thermally driven exit jets that emanate from deep canyons like Parley's and Weber. These winds tend to be confined to very near the canyon mouths and occur fairly frequently.

Downslope winds associated with flow across the Wasatch Crest and the development of high amplitude mountain waves. These winds occur less frequently, but can be much stronger and and affect a larger area.

Unfortunately, the term Canyon Winds, which makes some sense as a name for the former, continues to be used for the latter. Yup, this is Zombie meteorology. No matter how hard we try to kill Canyon Winds as a name for downslope wind events, it goes on like the living dead.

Like Napoleon, meteorologists know that nothing good comes from the east. Most of the time, our weather comes from the west, so when it comes from the east, the pattern is unusual and anomalous and strange things happen.

Wasatch Front residents are all too aware of what often happens when our flow comes from the east: downslope winds. Indeed, we will be seeing a downslope wind event develop later today and amplify tonight as the large-scale flow between a developing ridge over northwest North America and a closed low near southern California strengthens and becomes more easterly. This easterly flow is quite apparent in the NAM forecast valid 8 am MDT tomorrow (Friday) morning (although I've elected to show tomorrow morning, strong easterlies expected tonight too).

Source: weather.utah.edu

A closeup of the corresponding NAM 850 mb (~6500 ft) wind and temperature forecast for 1500 UTC (0800 MDT) tomorrow that time shows a low-level flow of cold air from interior Wyoming that is blocked by the Uinta Mountains and extends westward toward the Wasatch crest.

Flow across the northern Wasatch crest is expected to generate what meteorologists call a high-amplitude mountain wave, with strong flow from crest level plunging down the western face of the Wasatch Mountains and generating strong winds along the northern Wasatch Front as indicated schematically in the image below.

Source: Whiteman (2000)

One of the most challenging aspects of forecasting events of this type is determining the strength of the winds. Most of our computer models lack the resolution to fully resolve the influence of the Wasatch Mountains. We have some locally run models that do a better job, but these events are relatively rare, so we don't know how well calibrated that they are. Nevertheless, we glean what we can from the models, experience, and past events. Based on this knowledge, the National Weather Service High Wind Warning issued at 10 am this morning calls for easterly winds of 30–40 mph with gusts in excess of 70 mph.

Source: NWS

Right now we don't think this event will be as strong as the December 1st, 2011 event which featured a maximum gust of just over 100 mph near Centerville. Let's hope that's the case, but don't use it as a reason to be complacent as this is still a strong event (and one can't rule out something stronger even if that's not a likely scenario). Secure those objects that can become airborne during strong winds.

Wednesday, November 20, 2013

An extremely difficult forecast period is on tap for northern Utah meteorologists. The large-scale pattern is forecast to undergo rapid amplification with a major ridge developing over the northeast Pacific and northwest North America while a closed low forms off the coast of California. This can be seen in the forecast dynamic tropopause (jet-stream level analysis) in the top image of the loop below, which covers the period from 11 PM last night through 11 PM Friday.

These patterns are often difficult to forecast since the models really need to nail both the amplitude and the position of the developing systems in order to allow for a skillful assessment of local weather.

Potentially in play the next three days are two major forecast concerns. The first is the mountain snowfall expected later today and tonight. The challenge here is determining where the fragments of precipitation making it into the Great Basin will end up and the productivity of the front that sags into northern Utah Wednesday night and Thursday morning. My guess is 4–8 inches in the upper Cottonwoods, but there is a wide range of possibilities.

The second is the potential for downslope winds along the northern Wasatch Front Thursday night and Friday morning when the models are calling for the development of strong easterly flow across the northern Wasatch Mountains.

The forecast lead time is long enough that it is difficult to assess with confidence the strength of this event. Thus, it is best to keep an eye on the forecast from the National Weather Service Salt Lake City Forecast Office and perhaps take some cautionary steps to secure outdoor items that are prone to wind transport (trampoline owners you know who you are!) just in case.

Tuesday, November 19, 2013

Following up on yesterdays post, I wanted to point to a presentation given by University of Utah Research Associate Kerry Kelly that is available here and discusses the significant impact of wood burning on pollution in the Salt Lake Valley. The talk is based on Kelly et al. (2013), published in the Journal of the Air and Waste Management Association.

Here are the key points:

1. Wood smoke (and possibly cooking smoke) is likely the largest direct contributor (i.e., emitted from a source) to PM2.5 on winter days with PM2.5 > 20 ug/m3. Note that our PM2.5 comes from these direct emissions and from chemical reactions involving other gases generated by combustion (such as nitrogen oxide). The latter are typically referred to as secondary PM2.5.

2. Wood burning emissions are highly variable depending on their design, operations, and fuel, but they are far filthier than heating with natural gas.

The bottom line is that you can do some serious air quality damage when you burn wood in a stove or fireplace. Although there is no silver bullet when it comes to fixing our air quality challenges, reducing or eliminating wood burning in the Salt Lake Valley (and possibly elsewhere since there is some exchange of air between the counties) represents low-hanging fruit that can be plucked to improve air quality during wintertime inversions.

Monday, November 18, 2013

With fresh snow on the ground and clear skies currently over the Salt Lake Valley, you might not be thinking much about air quality today, but there is something that has been nagging at me since last week. Perhaps the photo below will jog your memory.

As far as Salt Lake air pollution events go, last week's wasn't a biggie, primarily because the inversion wasn't intense (lack of snow cover) or prolonged. Nevertheless, PM2.5 concentrations climbed throughout the week, with hourly averages peaking at 34 ug/m3 on the 13th and 24-hour averages peaking at 25 ug/m3 early in the morning on the 14th. The National Ambient Air Quality Standard (NAAQS) is a 24-hour average of 35 ug/m3. Although we did not reach this level, PM2.5 concentrations remained near or above 30 ug/m3 for much of the day on the 13th.

Source: Utah Division of Air Quality

Nevertheless, during the entire event we remained in the "unrestricted" category for air quality action. If you watched the news, you probably heard that you were good to go for using wood-burning stoves and fire places. I don't know about you, but I noticed the smell of smoke on at least a couple of occasions last week.

At issue is this: why not at least encourage the voluntary decision to not use wood and coal-burning stoves and fireplaces and take mass transit even during these moderate air quality events? I don't see this as a mandate, but simply an effort to encourage citizens to consider taking mass transit and avoid wood burning. What is the harm in that?

There is no single silver bullet to solve our air quality challenges, but a more proactive system to encourage voluntary actions to reduce emissions would help.

Sunday, November 17, 2013

Yesterday's storm delivered as promised. The Utah Avalanche Center reports 10-15 inches in the Ogden area mountains, 12-14 inches in the Park City Area Mountains, 18-20 inches in Big Cottonwood, and 15 inches in Little Cottonwood. The Alta-Collins automated stations recorded about 14 inches with 0.83 inches of SWE. This is in addition to the modest 2 inches that fell on Friday.

That's all great news, but I feel like I'm in a bit of a ski purgatory. Alta and Snowbird have closed for uphill skiing. Much of the terrain that had snow on it prior to the storm now has considerable avalanche hazard. Much of the lower angle terrain that I typically ski in such situations was snow free or nearly snow free prior to the storm, or requires access via routes that were previously snow free. Bony conditions abound. The Utah Avalanche Center notes that a couple of injured skiers were evacuated out of the Albion/Catharine's area yesterday.

Put some Black Sabbath on your iPod and channel Ronnie James Dio, but play it cautious. Both heaven and hell lie out there today.

Saturday, November 16, 2013

The storm is here and it is snowing in the mountains, but I'm "snowblind". Why? The KMTX radar is out!

Source: NWS

Apparently there has been a major hardware failure and it appears that we may be without radar for the entirety of the storm.

Source: NWS

This is a huge handicap for nowcasting. There's only so much you can do with satellite data, web cams, and precipitation gauge observations. The good news is that the returns thusfar are encouraging. Through 9am this morning Snowbasin's Middle Bowl observing site has observed 0.31 inches of SWE (all in the form of snow) since midnight. Alta-Collins 0.13 inches of SWE with ~3 inches of snow, which gives 5 inches since yesterday. Web cams show a beautiful scene at Albion Basin.

Source: Alta.com

The models suggest that mountain snow will continue through the day and into the evening. Let's hope it does as we could use a major dumpage. Be careful out there...

Friday, November 15, 2013

I love hiking in the early stages of a storm as the snow just begins to coat the ground, as was the case on my crack-of-dawn hike this morning. There's something therapeutic about being wrapped in a good hard shell, having good traction to keep up a vigorous pace, and having wet snowflakes tickle the face.

This morning's appetizer storm is also producing a beautiful scene up in the mountains, at least in the Albion Basin web cam at Alta.

Source: alta.com

The main course will arrive late tonight and tomorrow. The latest model runs are drier than yesterday. This morning's 12-km NAM has a forecast total accumulation from this morning through Sunday morning of 8.6 inches in upper Little Cottonwood compared with 20+ yesterday. The GFS is a bit drier as well. A big reason for the decrease is that the models are calling for the trough to be weaker and faster moving, and this ultimately puts the brakes on the post-frontal snowfall on Saturday night. Keep in mind that these models don't fully resolve the terrain of the central Wasatch, so accumulations are often (but not always) greater than advertised.

The loop below shows the progression of forecasts produced over the past few days by the GFS, all valid at 0000 UTC 17 November (1700 MST Saturday 16 November). Note the variations in the depth and timing of the trough, but how the more recent model runs have been producing a weaker trough.

Keep your fingers crossed that things hold together and that the trough delivers on Saturday.

Thursday, November 14, 2013

Numerical weather prediction models that are run on computers form the backbone of modern weather forecasting. Over the past few decades these models have improved dramatically as they have become increasingly sophisticated in terms of their formulation, ability to resolve smaller scale terrain and atmospheric effects, and use of satellite and other observational datasets.

Thus, critical to all forecasts is the use and interpretation of numerical weather prediction model output. Most forecasters use something called the forecast funnel to do this. The approach typically involves an assessment of the large scale atmospheric structure (such as the strength and movement of pressure systems and fronts) and then a funneling down through smaller scales until one is considering a very specific local forecast.

For a storm like the one expected this weekend, a forecaster examines data from several forecast models, such as the GFS, NAM, and ECMWF, as well as ensemble modeling systems like the SREF see Forecast Tools: The NCEP Models). Critical for this storm is the track and intensity of the upper-level trough digging down from the northwest and its interaction with the regional topography. Given that each of these models and ensemble modeling systems has differing strengths and weaknesses, all of them are typically consulted and considered.

Once the forecaster has a handle on the larger-scale flow and its interaction with the topography, they typically begin to look at smaller scales. We have some products on our Utah Weather Center web site that allows you to look specifically at what some of the models are predicting for upper Little Cottonwood Canyon. Some of this information comes directly from the model, such as QPF (this is the amount of precipitation in terms of snow water equivalent), while others such as snow ratio/water content and snow use algorithms developed by Alcott and Steenburgh (2010) applied to the model output. For instance, here is the forecast from the latest 12-km NAM (initialized at 1200 UTC this morning).

So, the 12-km NAM is generating a total of 1.48 inches of snow water equivalent through Sunday morning which, based on our algorithms, equates to 20 inches of snow. Although it calls for some light snow on Friday, most of this falls on Saturday and Saturday night (Note that the temperature, RH, and wind forecasts are for the top of Mt. Baldy, at 11,000 feet, which is very exposed and typically colder and windier than found across most of Alta).

Another way to look at this is graphically. You can find these plots on the Utah Weather Center if you click on the model of interest, then "meteogram", and then "Alta, UT."

Of course, other models produce differing amounts. The higher resolution 4-km NAM is calling for 15.5 inches (Addendum @ 10:40 AM: My bad...the 4-km NAM only goes through Saturday afternoon, so this total does not include the Saturday night period. Through 5 PM Saturday, the 4-km NAM produces 15.5 inches and the 12-km NAM 14.9 inches, fairly comparable). The GFS, which is fairly low resolution and thus doesn't usually fully capture the full enhancement over the Wasatch Range, only 6.4 inches.

This spread is produced because the atmosphere is chaotic and because we use somewhat different techniques to simulate the atmosphere in these various models. When you see a forecast of say 10-20 inches, that reflects the most likely range of possibilities. Typically that range also reflects some analysis and assessment of the model output, such as giving more weight to a model that the forecaster feels has a better handle on the situation, or making adjustments based on past model performance and biases. Forecast confidence is typically larger for shorter range forecasts than for larger range forecasts, but some phenomenon, such as lake effect, are very difficult to predict even with lead times of a few hours.

So, in a situation like this, we see a storm coming, but there remains some uncertainty with regards to magnitude. My best guess for the most likely range is 10-16 inches for upper Little Cottonwood, which is comparable to the NWS forecast issued 3 am last night. This is lower than predicted by the 12-km NAM, which reflects my concern that the trough will move out fairly quickly, bringing a quicker end to the storm.

So that's some insight into the forecast process, as imprecise as it is.

Wednesday, November 13, 2013

The model forecasts just seem to get better each day for this weekend's storm (with some mountain snow showers on Friday too). Let's hope that they aren't just teasing us and that Mother Nature will ultimately deliver.

Our potential savior system is an upper-level short-wave trough currently located just to the east of the Kamchatka Peninsula (X below). It is expected to roll over the long-wave ridge and then dig into the northwest United States.

The models have disagreed the past few days, but as things stand now, it appears that the GFS, NAM, and ECMWF agree that we will be seeing a storm on Saturday and possibly Saturday night (depending on how productive the post-frontal environment and lake effect prove to be). Further, this is an event that looks cold enough to bring snow to the valley floor.

It is a bit early to be thinking about snowfall amounts as a shift in the track of the upper-level trough could really screw things up (and perhaps the more excited we get, the more likely that is to occur!), but the models are currently calling for this to be a major event in the mountains. Here are some numbers from the latest NAM showing a bit of light snow on Friday when a weak trough moves through followed by much heavier precipitation late Friday night and Saturday.

Should the storm deliver, channel your inner Jedi and resist temptation to throw caution to the wind. All that weak, faceted snow currently on upper elevation slopes is just sitting there waiting for a load and a trigger. If the forecast pans out, the situation will be very similar to the November 13, 2011 "avalanche imbroglio" that featured at least 12 human triggered avalanches in upper Little Cottonwood Canyon, including one that killed professional skier Jamie Pierre. Click here to see and read the Utah Avalanche Center list for that day and remember that the terrain at the resorts is not currently subject to avalanche control and needs to be treated as backcountry.

Tuesday, November 12, 2013

One of the best ways to ensure a storm is to forecast dry weather, as done in the previous post (Snow(Making) in Forecast). I came in this morning, pulled up the latest GFS, and lo-and-behold, the forecast for this weekend had changed. Dramatically.

Here's the GFS forecast for Saturday afternoon that I used yesterday. We are in the wake of a dry trough passage.

And here's the GFS forecast from this morning for Saturday afternoon.

Yup, quite a change. Keep your fingers crossed we get something. Anything would make me happy at this point.

Monday, November 11, 2013

Mild weather remains in the forecast through tomorrow (Tuesday) when the warmest air of the current dry spell is expected to move over northern Utah and 700-mb (10,000 ft) temperatures over the Salt Lake Valley peak at about +5ºC. Tomorrow will be a good day for a foothill hike.

The past few days have been a serious setback for the snowpack. It's now a do over for the south-facing aspects, which are snow free. Snowmaking at the resorts has been limited or impossible. Fortunately the sun angle is low enough that upper-elevation north-facing aspects are retaining most of their snow.

Forecasts for the next seven days show a shift in the pattern after Tuesday with Utah under the influence of cooler northwesterly flow. The resorts should be able to get back to snowmaking, and I suspect they will be firing all the guns in their arsenals by later in the week when 700-mb temperatures are forecast to drop to near -7ºC.

I wish I could say that there was a big storm on tap, but as things look right now, that's not the case through next weekend. The models bring a couple of weak short-wave troughs through, but right now none of them look to produce more than a few mountain snow showers. Perhaps one of them will prove stronger than suggested by the models, but I'm not optimistic.

Sometimes there is hope in the extended, but the 8-14 day outlook from the Climate Prediction Center looks bleak.

Source: CPC

Of course, these long-range forecasts have only modest skill at best. Burn some skis and the pattern will change.

Saturday, November 9, 2013

My son and I got out for our first day of skiing today, opting for a "combat ski tour" at Alta where snow-covered (natural and artificial) north facing aspects were easily accessible. Instead of first tracks and chin ticklers, we experienced first scratches and bone rattlers, but any day that my back allows me to enjoy snow, sun, and turns with my son is priceless right now.

People in the snow business know that aspect is everything and that's very apparent right now. Even with the warm weather, there's little if any snowmelt on upper-elevation north facing aspects, but the south-facing aspects across from Alta are nearly snow free.

Friday, November 8, 2013

With the Sochi Games coming up this winter, I recently dug out my slides from the Nagano Games and did some reminiscing. The Salt Lake Olympic Committee (SLOC) sent me to Nagano to scope out weather observing and forecasting needs for the 2002 Olympics. Being a pre-911 Olympics, I had credentials that provided unfettered access to the venues and a first-hand look at the events and weather needs for four jet-lagged days. Most observation days involved a group visit and tour of a venue, watching an event, and then meeting with the venue meteorologist. At a few venues, I met with former Olympians, coaches, or other support individuals to discuss the impacts of weather on the competitions. Given the "boring" weather in place over Utah right now, I thought I'd share a few photos and perspectives.

Enjoying a sunny day with Wasatch touring legend Dave Hanscom at the Snow Harp cross country venue in the Hakuba Valley. The Japanese Alps rise more than 2000 meters above the valley floor and receive abundant "lake-effect" snowfall from the Sea of Japan.

29-time Olympic and World Championship medalist Bjorn Daehlie chasing an Italian-team skier during the third leg of the men's 4x10km relay. After losing to the Italians in Lillehammer, Daehlie and the Norwegians claimed a 0.2 second victory in Nagano thanks to a sprint in the anchor leg by Thomas Alsgaard. What a race!

Deep-powder skiing with a few security guards after cancellation of the Super-G. The hill was largely mine and I enjoyed a few chin ticklers on the closed and deserted downhill course.

Vending machines in Hakuba. Surprisingly, we didn't see such hospitality during the Salt Lake Games.

The weather operations center in Nagano. I had a translator work with me here, which was great, except for techy terms like parameterization, polarimetric, grid-spacing, etc.

The venue forecaster at the Hakuba Ski Jumping Center. This is one of the most challenging forecasting positions at the Winter Olympics because ski jumping is extremely sensitive to even small changes in wind speed and direction.

Thursday, November 7, 2013

Many people don't realize that the Great Salt Lake is a divided body of water, with each half operating almost independently from the other.

This is not the natural state of affairs. For centurys, water in the Great Salt Lake could move freely and without restriction. Then, in the late 1950s, the railroad built an earthen causeway across the lake. Although a couple of culverts were added to enable some mixing between the two haves, they have remained only loosely connected for many years and their chemical composition is dramatically different. Most of the freshwater inflow to the Great Salt Lake enters the south half, so the salinity is lower (typically 9–12%) than found in the north half (typically ~28%). This leads to differences in algeal and bacterial and water color between the two halves that can clearly be seen from space and the ground.

The Great Salt Lake from space. Source: NASA S135-E-006466.

The Salt Lake Tribune reports this morning that the two culverts have been in a state of decay for many years. One needed to be plugged last year, the other is currently failing and needs to be plugged for the railroad to continue operations. This will fully divide the lake once again. There are discussions about putting in a 180 ft bridge (yet to be designed) to reenable some flow between the two halves.

How to deal with this causeway issue is a remarkably complex question. Lake salinity will be strongly influenced by how much water can flow between the two halves, with direct ecological and economic consequences. Thus, I expect this will be a contentious issue and a remarkable case study in the management (or mismanagement) of coupled human and natural systems.

About Us

The Wasatch Weather Weenies discuss the weather and climate of the Wasatch Front and Mountains, western United States, and beyond.

Participants include aspiring and old-school atmospheric scientists, weather enthusiasts, powder snobs, and poor souls enrolled in classes taught by University of Utah Atmospheric Sciences Professor Jim Steenburgh. Many posts feature content or insights enabled by the support of the National Science Foundation, Office of Naval Research, and the NOAA/National Weather Service.

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